Natural gas, like other forms of heat energy, is measure in British Thermal units, or BTU. One BTU is equivalent to the heat needed to raise the temperature of one pound of water by one-degree Fahrenheit at atmospheric pressure. Because LNG is sold in accordance with its BTU value, accurate analysis of the BTU value of any particular LNG shipment, as well as analysis of the constituent components of the LNG, as it is loaded on and off a respective tanker ship is crucial. For example, to determine an expected price for a particular shipment, when LNG is loaded onto a tanker ship at an overseas location, such as Trinidad and Tobago, the supplier calculates the BTU value of the LNG as it is loaded into the hull of the ship. Thus, the operator of the tanker ship carrying the LNG shipment is keenly interested in accurate BTU measurement of both the loaded LNG as well as the off-loaded LNG as the shipper typically burns the LNG vaporized in transit to run the ship and, thus, is responsible for cost of the LNG vaporized in transit.
Presently, if a LNG tanker is being loaded from multiple storage tanks or a series of railroad tanker cars, using, for example, two to four different pipelines, there is no device or method to generate accurate composite data from the combined inputs and account for variations in flow rates of each of the discrete inputs during the transfer/loading process. This problem applies similarly in the context of one or more tankers and/or railroad tanker cars using multiple pipelines to load one or more tanks and/or one or more railroad tanker cars.
In the context of a cryogenic LNG, for example, cargo loads are often composed of simultaneously transferred inputs from different storage vessels containing different compositions or other physical properties. The flow rates may vary between the input from respective sources, which leaves the operator to essentially guess or guesstimate the contributions from each source and apply that obtained estimated number to the determined energy content/composition analysis of the resulting transferred mixture.
When time-elapse composite sampling of a multi-input mixture is processed through a composite system as along the lines of that described in U.S. Pat. No. 9,562,833, the use of relative flow rate guesstimates for analytical purposes becomes unreliable, imprecise and untenable.